C# Best way to replace x repeated tokens by one token

Question

If I have:

Some text



More text






Even more text

What is the more elegant way to obtain:

Some text

More text

Even more text

All with knowing the number of repeated tokens

Answer 1

Use regular expressions. Match the entire string '\r\n' and replace with a single '\r\n'

The function you need:

pattern = "(\\r\\n)+";
Regex rgx = new Regex(pattern);

newString = rgx.Replace(oldString, "\r\n");

EDIT: Apologies for missing the + earlier

Answer 2

Perhaps something like:

var result = string.Join("\r\n", s.Split(new[]{"\r\n"}, StringSplitOptions.RemoveEmptyEntries))

Answer 3

I don't know C# syntax, but just use a simple regex to replace (\r\n)+ with (\r\n)

Answer 4

The method to do so using regular expressions would be

string replaced = System.Text.RegularExpressions.Regex
    .Replace(input, @"(?:\r\n)+", "\r\n");

(The (?:...) syntax is a non-capturing group, which can be replaced with a capturing group (just (...)), but that is slightly less efficient and not more readable, IMO.)

Answer 5

You can use a regular expression:

str = Regex.Replace(str, "(\r\n)+", "\r\n")

Another way could be to split on the line breaks removing empty entries, then join again:

str = String.Join("\r\n", str.Split(new string[]{"\r\n"}, StringSplitOptions.RemoveEmptyEntries);

Consider if you should use the string literal "\r\n" or the Environment.NewLine constant. That depends on where the data comes from.

Answer 6

If the \r\n means what it usually does, you're replacing successive blank lines with a single blank line.

I'm sure there are tools for that purpose. I wouldn't know about C#, though.

Answer 7

Without Regexs (which make my head hurt)

    string RemoveRepeated(string needle, string haystack)
    {
        string doubleNeedle = needle + needle;

        while (haystack.IndexOf(doubleNeedle) >= 0)
            haystack = haystack.Replace(doubleNeedle, needle);
        return haystack;
    }

Answer 8

The fastest way:

Regex reg = new Regex(@"(\r\n)+");

string replacedString = reg.Replace("YOUR STRING TO BE REPLACED", Environment.NewLine);

Answer 9

Just a few days ago, there was nearly the same question around here in SO. There was not a NewLine the problem, instead it where whitespaces.

There was also the one guys who prefers the Split, Join method and the other site using a regex. So Jon made a comparison between both and it came out that a compile regex was much faster.

But i just can't find this question again...